Electric machines, e.g., multi-phase electric motor/generators, have stator windings that are energized by alternating current from inverter modules that electrically connect to high-voltage DC electrical power buses. During specific operating conditions, including high-speed, low or no load conditions, an electric machine, e.g., a permanent magnet (PM) motor may operate in an uncontrolled generator (UCG) mode, wherein motor back-emf increases, resulting in a motor output voltage that is greater than voltage on the high-voltage bus. Back-emf (electromotive force) refers to voltage generated in an electric motor caused by motion of an armature in relation to magnetic fields from field magnets or windings, with such voltage being related to motor speed and other factors. Back-emf is a separate effect from motor inductance. This excess output voltage may result in a charging current flow through one or more of the diodes arranged in parallel to the switches of the inverter to the high-voltage battery. The charging current flow occurring in the UCG mode may result in excess current through components of the inverter or overcharging of the high-voltage battery that can negatively affect service life of the inverter or the high-voltage battery. Designers may select electrical component design factors and derating schemes that comprehend occurrence of excess charging in the UCG mode.